Islanding Detection in Electric Distribution Circuits using Multiple-Model Filters in the Presence of Multiple PV Inverters

A passive, inverter-centric method for islanding detection using multiple-model filtering (MMF) is presented in the presence of multiple photovoltaic inverters (PVIs). Islanding is the situation that parts of power distribution circuits are disconnected from the grid by switches for protection from the effects of faults while the disconnected circuits are still being energized by active sources, including solar PVIs. The purpose of the MMF- based islanding detection is to timely inform a behind-the-meter grid-connected PVI whether to trip itself offline or to stay grid-connected with minimum communications. Detection filters are built based on all anticipated circuit models corresponding to switch states observable by the PVI, and a weighted local measurement residuals is used to obtain model probabilities. An autocovariance least-squares method is adopted to estimate the process and measurement noise covariance matrices of each filter design model. Two scenarios are detailed for a modified Roy Billinton Test System (RBTS): i) multiple PVIs are located along the same radial circuit (feeder), and ii) multiple PVIs are located at different feeders. The minimum communication requirements among the PVIs are determined for successful islanding detection.